Modern elevators are typically arranged to prohibit unintended car movement, i.e. non-commanded movement of the car with doors open within the door zone away from the landing.
This is implemented by providing the elevator with a means to stop the unintended car movement. These means may comprise a brake as well also an equipment activating the mechanical brake. Generally, the unintended car movement protection function (UCMP) can be divided into the following parts: detection equipment, activation equipment and stopping equipment. The detection equipment is configured for detecting occurrence of the unintended movement e.g. using a sensor, the activation equipment is configured for activating a stopping equipment, and the stopping equipment, such as a mechanical brake, is configured for executing the actual braking.
The function of the UCMP includes several actions occurring in a sequence. For swift and effective operation of the UCMP, it is important that the detection equipment appropriately swiftly triggers said activation, and said activation equipment appropriately swiftly activates the stopping equipment, and said stopping equipment appropriately swiftly performs braking of the car. It is possible that different failures or wear of the components, which cannot be detected by normal inspection or normal diagnostics in an inspection by a service person, can cause that the UCMP works too slowly and cannot stop the car within a desired distance. Such an effect can result from any delay formed in the operation of the system components at any point of the sequence. Such as delay can be formed in releasing of safety relays of the door zone, or releasing of main contactors or equivalent component used for activating the stopping equipment. Such an effect can result from failure of a DC-side circuit breaking component (e.g. relay) of the brake controller, for instance. Such an effect can also result from brakes becoming slower to drop. Accordingly, performance of the elevator braking system in emergency situations or other abnormal situations, and in particular the UCM situations, is not constant. In order to ensure safety, it would be advantageous to receive information describing state of these functions of an elevator. A drawback of the known elevators is that no information is received describing performance of the elevator braking system in said situations where swift braking is needed.